Breivik told his trial he planned to film the beheading and post the video on the internet - as well as kill all 600 people who were at the Labour Party's youth camp on July 22.

But Brundtland had already left the area as the far-right fanatic began his shooting spree.

The revelation came as Breivik described how he became a deadly marksman by honing his gun skills by playing the violent Call Of Duty: Modern Warfare computer game. The mass killer even bought a special gun sight used on the game - and attached it to the hunting rifle he used for his deadly rampage on a Norwegian island.

Thomas Hylland Eriksen, a professor of social anthropology at the University of Oslo, said such computer games could put Breivik in a state of delusion.